District heating efficiency gains applied to decentral heat pumps

[cpschau]

In add_brownfield, the COPs of the heat pumps built in the previous planning horizon are supposed to be updated according to the efficiency gains in district heating due to decreasing supply temperatures. However, this COP update is also applied to all decentral heat pumps, that are also indexed with n_p.links.index[n_p.links.index.str.contains("heat pump")]. Instead, exclusively the urban central heat pumps should be indexed adjusting the string query or using the carrier column.

Furthermore, even the COPs for district heating should be considered to change not only based on the supply temperature dynamics but also the technological efficiency gains.

https://github.com/PyPSA/pypsa-eur/blob/c7c664d3d7e3e8a3141fb7960d6488e7b2ba240e/scripts/add_brownfield.py#L245-L247